Heals and Shields increase your effective health, which is not included in the damage calculations, and thus is effective in mitigating % hp true damage.
So champs like 
, who all have either large shields or large heals, can work very well against it, as well as 
.
Old Man Teeto2 votesIt's actually amusing, but true.
Champions who can create large shields that act as health, without actually having to increase their actual health (which would increase the amount of true damage they take) are surprisingly effective at protecting against this damage.
However, I wouldn't list Nautilus, since his shield strength scales off his max health, so it's sorta a catch 22.
KONO RUBICK DA2 votesheals and shields counter everything, normal damage would be countered by defense AND heals and shields
Lord Boltrix1 votesSo a champion who can heal and who can shield consistently enough to defeat Vayne and Fiora would be best?
Bârd2 votesIt is one component, yes.
As a mechanic, that is how you can beat it, but you are better off working off of the counterplay of the champion itself, rather than just relying on a shield to save your ass.
Take for example
Against 
, he would just CC her to death while revealing her with 
and tanking her with W.
Against 
, he can bait out her Riposte with ult (or wait until an ally does so), and since she immobilizes herself in doing so, sets up an easy Q into a chain of CC while your teammates fuck her up.